1. Field of the Invention
The present invention relates to a method of detecting a residual quantity of ink, a printing device, a program and a storage medium for calibrating an optical sensor.
2. Description of the Related Art
As a method of detecting a residual quantity of ink in an ink tank for an ink jet printing device, there is known a method of detecting a residual quantity of ink by sensing a reflection coefficient of a specific part of the ink tank changing with presence/absence of the ink by an optically reflective sensor (Japanese Patent Laid-Open No. 2000-43287).
In a case of the ink jet printing device, however, ink is ejected for printing at the time of carrying out the printing and therefore, ink mist generated inside the printing device may be possibly attached to the optical sensor. In consequence, as in the case of Japanese Patent Laid-Open No. 2000-43287, in a case of reading the reflection coefficient of the specific part of the ink tank by the optically reflective sensor, when the optical sensor is contaminated with the ink mist, the sensor may not possibly read the reflected light accurately. Besides, a detection characteristic of the optical sensor possibly largely changes due to aging or a deviation in optical mechanism accuracy of the optical sensor.
Therefore, for securing detection accuracy in an ink residual quantity at more than a predetermined level even if such a change of the detection characteristic occurs, there is known a method of carrying out calibration of the optical sensor to detect the ink residual quantity (U.S. Pat. No. 5,975,665). This method is a system which is provided with a circuit for being capable of adjusting sensitivity of the optical sensor and a reflective object for calibration disposed on a carriage, the sensitivity of the optical sensor a characteristic of which has changed by the object at the time of detecting the ink residual quantity is adjusted to a given level and the detection characteristic is corrected for securing detection accuracy.
However, the method of U.S. Pat. No. 5,975,665 has still the problem. Since the reflective object used for calibration of the optical sensor is installed inside the ink jet printing device, the reflective object is possibly contaminated by the ink mist. If the reflective object is contaminated, the detection characteristic by the calibration may possibly change depending on degrees of the contamination. Accordingly, since the contamination degree regularly changes caused by use of the ink jet printing device, the sensitivity of the optical sensor may not be possibly adjusted to a given level by calibration or an erroneous determination may be possibly made as to detection on presence/absence of ink, depending on the contamination degree of the reflective object.